BEIRUT -- The Muslim Eid al-Adha holiday was marked with the death of more than 20 people in an explosion in the southern Syrian province of Dara, government and opposition forces said Wednesday, and rebel factions in the area announced a break with the major U.S.-backed opposition coalition.

And, in another indication of the increasingly complex nature of the Syrian conflict, the Turkish press reported that Turkish military units positioned along the Syrian border returned fire from Al Qaeda-linked fighters in the strategic northern Syrian town of Azaz, three miles from the Turkish frontier.

Militant Islamist rebels overran Azaz a few weeks ago. But fighting between rival rebel factions continues in and around the town, with some errant shells apparently landing in nearby Turkey. Ankara has a policy of responding to any artillery or mortar rounds that land on Turkish territory from Syria.

In southern Dara province, each side in the Syrian conflict blamed the other for the deaths of at least 21 people, most of them apparently civilians, in a bomb blast that occurred Tuesday but was widely reported a day later.

The southern province is where antigovernment demonstrations erupted more than 2 1/2 years ago, detonating a national protest movement that evolved into a civil war. The conflict has left more than 100,000 people dead and much of the country in ruins.

According to opposition accounts, a mine along a road in the town of Nawa destroyed a bus carrying civilians fleeing from government bombardment nearby. Opposition advocates said the government laid down mines in the area to protect nearby installations under rebel siege.

"The civilians did not know the road was mined," said Omar al-Hariri, an opposition activist in the area reached via Skype.

The official Syrian Arab News Agency, however, reported that "21 terrorists fell as they were trying to booby-trap a car." The Syrian government routinely calls the opposition forces "terrorists."

Dara province, along the Jordanian border and 60 miles from Damascus, the capital, is a crucial battleground in the Syrian conflict. In recent weeks, both the government and rebels have proclaimed advances in the area.

On Wednesday, a video emerged from more than 60 rebel brigades in the Dara area declaring that they would no longer recognize the authority of the U.S.-backed Syrian National Coalition, the opposition umbrella group. The rebel factions accused the coalition of having “neglected the tenets of the homeland."

The statement follows similar rejections of the U.S.-backed coalition from rebel brigades based in northern Syria and in the suburbs of Damascus. Al Qaeda-linked rebel factions have also refused to recognize he authority of the opposition coalition, which is mostly based in neighboring Turkey.

The umbrella coalition says it still maintains support of Free Syrian Army brigades throughout Syria.

The ever-deepening fractures in the Syrian rebel ranks have raised questions about who will represent the opposition if the so-called Geneva II Syrian peace talks, brokered by Russia and the United States, ever take place. U.S. and Russian officials have voiced hope that the Geneva II negotiations could be held next month, but no date has been set.

BEIRUT — Syrian officials said Sunday that authorities working with the Red Crescent had overseen the evacuation of 3,000 women and children from a battleground suburb of Damascus to temporary shelters outside the war zone.

BEIRUT — Suicide attackers detonated a pair of car bombs in central Damascus on Sunday near the state broadcasting headquarters, causing material damage to an exterior wall but no injures, the Syrian media reported.